1. Field of the Invention
The present invention relates to processes for making organic electronic devices. The invention further relates to devices made by such processes.
2. Background
In organic electronic devices, such as light-emitting diodes (“OLED”), that make up OLED displays, the organic active layer is sandwiched between two electrical contact layers in an OLED display. In an OLED the organic photoactive layer emits light through the light-transmitting electrical contact layer upon application of a voltage across the electrical contact layers.
It is well known to use organic electroluminescent compounds as the active component in light-emitting diodes. Simple organic molecules, conjugated polymers, and organometallic complexes have been used.
Devices which use photoactive materials, frequently include one or more organic charge transport layers, which are positioned between the photoactive (e.g., light-emitting) layer and one of the contact layers. A hole transport layer may be positioned between the photoactive layer and the hole-injecting contact layer, also called the anode. An electron transport layer may be positioned between the photoactive layer and the electron-injecting contact layer, also called the cathode. Fabrication of organic electronic devices by solution processing techniques, such as spin-coating or ink-jetting, can have manufacturing advantages over vapor deposition techniques. In the field of OLEDs, multilayer devices have demonstrated performance advantages over simple one-, or two-layer devices. Multilayer OLEDs with small organic molecules are generally fabricated by vapor deposition techniques. Multilayer polymeric OLEDs have been fabricated by solution processing techniques using one water-soluble organic material and one solvent-soluble organic material. For example, a transport layer of poly(ethylenedioxythiophene)/polystyrenesulfonic acid (“PEDT/PSSA”) is formed from an aqueous medium and overcoated with a light-emitting phenylenevinylene polymer in an organic solvent.
The fabrication of multilayer OLED devices with organic light-emitting materials by non-aqueous solution processing or the combination of vapor deposition and non-aqueous solution processing techniques has generally been unavailable. The organic materials that are useful with such light-emitting materials generally have similar solubility properties in most organic liquids.
There is a continuing need for processes to form organic electronic devices.